Hydraulic hose fittings are used to connect hydraulic hoses, tubes, and pipes to pumps, valves, cylinders and other parts of the hydraulic system. So what happens if you pick a wrong fitting? Pressure drops and leaks will become your best friends. Unfortunately, something as small as a fitting can quickly decrease the efficiency of the whole hydraulic system. If you get too overwhelmed with the shapes, materials, threading, and sealing options to choose from, save your time, and check our guide on how to pick the right fitting best for your job.
Hydraulic Hose Assembly Explained
For many of us, the first time we have to decide on which type of hydraulic hose fitting to use is during the hose assembly. Crimping is the most popular method assembling the hydraulic hose. It is always a good idea to ask yourself five major questions about S.T.A.M.P.E.D. (size, temperature, application, materials/media, pressure, end, and delivery of your hose) before you get started with any hose assembly. After all the specifications have been defined, the crimping machine is set to the appropriate crimping diameter setting. Then the hose assembly specialist lubricates the fitting, pushes it inside the end of the hose and inserts it into the crimper dies. Finally, the hose is actuated to close the dies and secure the fitting permanently onto the hose. The hose assembly specialist would be able to assist you in finding the best fitting and assist you with any questions.
Materials Hose Fittings Are Made Of
Hoses, as well as fittings, come in many different types and materials. Importantly, the material used for the hydraulic hose fitting defines its properties. Most common fittings are made of plastic, steel, stainless steel, copper, brass or aluminum.
Plastic fittings generally are considered more resistant to the corrosion but are weaker and less durable. Therefore, they are the least popular choice when it comes to hydraulic applications despite their low price. Due to the high-pressure ratings, metal fittings are a better fit.
Steel fittings come as a mix of iron with some other metals to make them more durable and improve the resistance to the heat. For example, carbon steel fittings made of the mixture of iron and carbon can withstand the temperatures from -65°F to 500°F.
Stainless steel fittings are used when the temperature range required for the job is -425°F to 1200°F. They are an excellent choice for highly corrosive environments. Usually, they are rated up to 10,000 psi. Some of the stainless steel fittings with special designs can be rated up to 20,000 psi. However, the high price makes them less affordable, so other alternatives are usually considered.
Copper fittings are corrosion resistant and have antibacterial properties. They are widely used in plumbing, heating, and cooling projects.
Brass fittings are less strong and durable than stainless steel. They can provide a leak-free operation and meet SAE, ISO, DIN, DOT, and JIS standards. Brass fittings temperature range is -65°F to 400°F. They accommodate pressure up to 3000 psi, but lower pressure ranges are usually recommended.
Aluminum fittings have a higher pressure rating than brass. They are lightweight and corrosion-resistant. They can handle the temperatures from -325°F to 400°F and the pressure range up to 4000 psi. Due to their low weight, they are commonly used in military, aerospace, and automotive industries.
Types of Hydraulic Hose Fittings
The two main categories include:
Permanent Crimp Fittings – the most common type of fittings. They require a presence of the crimping machine to attach a hose to a fitting.
- Re-Usable Fittings – quick disconnect fitting, also known as quick couplings. They are an excellent choice if you do not have access to the crimper provided that your hose is ‘field attachable fitting’ compatible.
Depending on the shape of the hydraulic fitting, they classified into:
Seven Things to Consider When Picking the Hydraulic Fittings:
The Security of the Connection Including Sealing Type
With the modernization of your equipment usually comes higher operating pressure. To address high operating pressure, more and more of our customers prefer to use O-ring seals. They are more resistant to cracks. O-ring seals also prevent the risk of over-torqueing and leakage. In terms of material stainless steel hose fittings have the highest pressure rating.
Vibration affects hydraulic plumbing and can shift the torque and cause fatigue. Remember to inspect areas with high vibration for leaks and damage.
Chemical Compatibility and Operating Fluid
A rule of thumb says that hose inner tube, cover, fittings and O-rings should be chemically compatible with each other. Pay extra caution when selecting a hose for gaseous applications, especially if there is a chance of permeation in order to avoid explosions, fires, and exposition to the toxic fumes. Always check with the manufacturer if the components of your hydraulic system are chemically compatible. Additionally, pay close attention to your seal being compatible with the type of hydraulic fluid used in a system. The Guide for Chemical Resistance Information from Parker can be found here.
It all goes great until you need a replacement fitting and the lead time is a couple of weeks, and you need it now. Usually, most NPT and JIC fittings are widely available and have many configurations to choose from. Hence, choose the fittings that are easier to find or stock up if you use any specific fitting with longer lead times.
Be careful is you use NPT (National Pipe Taper) pipe threads fittings. Even though it sounds easy to fix the leak with this type of fitting by tightening the connection, you increase the risk of getting a crack in the fitting. Use O-rings with the elastomeric seals such as DIN 2353, SAE J1453 to prevent the risk of unexpected leaks and switch to DIN (German Institute for Standardization) metric fittings in order to avoid overtightening. If you use elastomeric seals, keep your temperature conditions within the recommended range. Unfortunately, even a single over-temperature event can damage all the seals and cause multiple leaks.
The temperature range for tube fittings is defined by three factors: material, plating, and seal if used. For leak-free operation use O-ring seals if the operating temperature allows you. Check the table below for the temperature range for the most common fitting and seal materials.There are special options available if you need hydraulic hoses and fittings to work under extreme temperature conditions. Contact us to learn more.
Mixing and Matching
Both SAE and ISO do not recommend mixing components of the hydraulic system from different manufacturers. Besides, Parker does not take responsibility for other manufacturers fittings compatibility with Parker hose. Therefore, if you intermix your hose and fitting from two different manufacturers, you void you hose assembly guarantee and increase the risk of the leakage.
It is important to remember to inspect your hoses and fittings for a secure connection and any leaks every couple of months. Even new fitting, if it was selected wrong, can cause problems. Although picking a hydraulic fitting sometimes feels like rocket science, if you follow our simple guides, it should not be a problem anymore.
If you want to read more about the most common hydraulic mistakes and how to fix them, click here.